1. Field of the Invention
The present invention relates to a printing element substrate, printhead, and printing apparatus.
2. Description of the Related Art
An inkjet printing apparatus typified by a printer includes a printhead which prints on a printing medium. The printhead includes a printing element substrate. Printing elements for printing based on print data, and driving transistors for driving the printing elements are arranged on the printing element substrate.
The printing elements and driving transistors are interposed between a power supply line and a ground line. At the time of printing, potential fluctuations may occur on the power supply line. The potential fluctuations become more serious as the number of printing elements to be simultaneously driven increases. The printing element substrate needs to adopt a circuit arrangement considering the potential fluctuations.
Japanese Patent Laid-Open No. 2002-355970 discloses an arrangement in which printing elements and driving transistors, and a control unit configured to supply a control signal to the control terminals of the driving transistors operate using different power supplies. In this arrangement, a control signal of a constant potential is supplied to the control terminal of the driving transistor, and the amount of current supplied to the printing element is hardly influenced by the above-mentioned potential fluctuations of the power supply. However, Japanese Patent Laid-Open No. 2002-355970 does not disclose that an element configured to supply a constant current to the printing element, and an element configured to control the printing element are arranged individually.